During delivery of household necessaries or other important articles, the contents are wrapped by an air bag so as to prevent the contents from being damaged by external impacts.
In the appended drawings, FIG. 1 is a perspective view showing a general air bag, FIG. 2 is a vertical sectional view taken along the line A-A of FIG. 1, which shows a valve of the air bag shown in FIG. 1, and FIG. 3 is a plan view showing a valve of the air bag to which air is not injected.
As shown in FIG. 1, the air bag 10 has a valve 20 that is closed by an inner pressure of air injected into the air bag.
Hereinafter, the general air bag is explained in detail.
The air bag 10 has a rectangular structure, and an air input channel 11 is formed along one side of the air bag 10. Also, a plurality of air pillars 13 are perpendicularly formed with respect to the air input channel 11. A plurality of valves 20 respectively connect the air input channel 11 to the air pillars 13, so air supplied through the air input channel 11 is introduced to each air pillar 13 through the valves 20. If the air pillars 13 are filled with air, inner pressure is generated to press the valves 20, thereby sealing the air pillars 13 such that the air in the air pillars 13 does not go out through the valves 20.
Referring to FIGS. 1 to 3, the air bag 10 includes two outer sheets 15 that form an overall configuration of the air bag. Also, the valve 20 is formed by two inner sheets 21 positioned inside the two outer sheets 15, a plurality of thermal bonding lines 31, 32, 33, and thermal bonding points 41, 42.
As shown in FIGS. 1 to 3, a plurality of heat resistance inks 23 are discontinuously applied to any one of facing surfaces of the two inner sheets 21 in a length direction thereof. Here, the length direction of the inner sheets means a direction perpendicular to the thermal bonding line 33. Each heat resistance ink 23 is formed to cover the air input channel 11 and the air pillar 13 with respect to the thermal bonding line 32.
In a state that the two inner sheets 21 are positioned in the two outer sheets 15, the air input channel 11 is formed by a first thermal bonding line 31 and a second thermal bonding line 32, positioned in parallel with each other. The second thermal bonding line 32 is formed while passing the heat resistance inks 23 discontinuously formed along the inner sheets 21. And, the first thermal bonding line 31 bonds only the two outer sheets 15.
The air input channel 11 is formed along the first thermal bonding line 31 and the second thermal bonding line 32 as mentioned above, and one side of the air input channel 11 is closed by thermal bonding and the other side is opened. Air is injected through the other side that is open.
Meanwhile, the outer sheet 15 and the inner sheet 21 are bonded by the second thermal bonding line 32, but regions where the heat resistance inks 23 are formed are not bonded. Thus, the air injected through the air input channel 11 is introduced to the air pillars 13 through passages 25 between the inner sheets 21, which are not thermally bonded due to the heat resistance inks 23.
In addition, the air pillars 13 are formed by third thermal bonding lines 33 extending perpendicularly from the second thermal bonding line 32. The third thermal bonding lines 23 are alternately formed with the passages 25 formed by the heat resistance inks 23. In other words, one passage 25 is formed with respect to one air pillar 13 by means of the discontinuously applied heat resistance inks 23. The air introduced to the air pillar 13 through the passage 25 fills the air pillar 13 formed by the third thermal bonding line 33.
Meanwhile, in a region of two inner sheets 21 positioned toward the air input channel 11 with respect to the second thermal bonding line 32, one inner sheet 21 and one outer sheet 15 are bonded and fixed to each other by means of the first thermal bonding point 41. As two outer sheets 15 are expanded due to the injected air, the inner sheets 21 bonded and fixed by the first thermal bonding point 41 become wider in opposite directions to open the passage 25.
However, the two inner sheets 21 positioned toward the air pillar 13 with respect to the second thermal bonding line 32 are bonded and fixed to any one outer sheet by the second thermal bonding point 42 to close the valve 20 by the air filled in the air pillar 13.
Thus, when air is injected to the air input channel 11, the air is introduced to the air pillars 13 through the passages 25, and the passages 25 are closed due to the inner pressure of the air pillars 13.
In the air bag described above, the discontinuously applied heat resistance inks 23 should be respectively matched with the air pillars 13 at accurate locations. However, while thermal bonding lines and thermal bonding points are formed in four sheets, deviation of location may occur in any sheet. Also, the sheets may be expanded due to the heat caused by thermal bonding, so it is difficult to form thermal bonding lines and thermal bonding points such that heat resistance inks are in accurate correspondence to air pillars. Due to this difficulty, workability is deteriorated, and an inferiority rate is increased.